Now, I don't as much have an idea for an entire event, but I like a lot of the ideas I've seen here.
I'm more partial to a more peaceful, character development-focused story however.
But I did have an idea that could be included in almost any kind of bigger picture event. I've seen posts on the internet of a game called "SHATNER."
Now, the game itself isn't my idea, but the random twist of events by writer-determined queues could make any story interesting. We could come up with a short-list of changes to make and writers could interject them into stories at their discretion.
This would only apply to open threads, not private ones, of course, but imagine you're RP is going just fine and someone posts "There's a speeder crashing right towards you!" or "You've been shot in the leg!"
We would of course throw limitations on what could be done, but it could easily keep writers on their toes to have random curveballs thrown at them. Also, these curveballs could easily be designed to fit with the RP Event itself.
For example, if the story is one of these ideas for a virus, you could go into someone's open thread and while they're eating their breakfast, just post "Suddenly So-And-So feels an itch in his throat and coughs, peppering his hand with blood. He knew then he'd been infected."
Bam, just like that. And then the writer has to roll with it. This seems like a good enough community we could pull that off without people abusing one another.
I feel this was poorly explained, but I tried. lol